I think I would avoid that one. The early 120s were some of the engines that gave YS's a reputation for being finicky. One of the fellows who does YS support in the YS forum here at RCU said something to the effect of not wanting to own any of the 120NCs, if I remember correctly. You'd probably get a better answer there.

If it was left with fuel in it ten years ago, you'd probably have to replace the regulator diaphragm, some gaskets, and the bearings (if rusty). I know I wouldn't pay much for it. If you buy it, you're just taking a good chance that you'll have to dump some money into it. There are plenty of good deals to be had on more recent YS engines. I bought a new 91AC (which is at least six or seven years old) last week for $160. I figured being new I wasn't taking too many chances. It showed up on Saturday and is in fine shape.